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Yap-Chiongco MK, Bergmeier FS, Roberts NG, Jörger KM, Kocot KM. Phylogenomic reconstruction of Solenogastres (Mollusca, Aplacophora) informs hypotheses on body size evolution. Mol Phylogenet Evol 2024; 194:108029. [PMID: 38341006 DOI: 10.1016/j.ympev.2024.108029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 01/24/2024] [Accepted: 02/05/2024] [Indexed: 02/12/2024]
Abstract
Body size is a fundamental characteristic of animals that impacts every aspect of their biology from anatomical complexity to ecology. In Mollusca, Solenogastres has been considered important to understanding the group's early evolution as most morphology-based phylogenetic reconstructions placed it as an early branching molluscan lineage. Under this scenario, molluscs were thought to have evolved from a small, turbellarian-like ancestor and small (i.e., macrofaunal) body size was inferred to be plesiomorphic for Solenogastres. More recently, phylogenomic studies have shown that aplacophorans (Solenogastres + Caudofoveata) form a clade with chitons (Polyplacophora), which is sister to all other molluscs, suggesting a relatively large-bodied (i.e., megafaunal) ancestor for Mollusca. Meanwhile, recent investigations into aplacophoran phylogeny have called the assumption that the last common ancestor of Solenogastres was small-bodied into question, but sampling of meiofaunal species was limited, biasing these studies towards large-bodied taxa and leaving fundamental questions about solenogaster body size evolution unanswered. Here, we supplemented available data with transcriptomes from eight diverse meiofaunal species of Solenogastres and conducted phylogenomic analyses on datasets of up to 949 genes. Maximum likelihood analyses support the meiofaunal family Meiomeniidae as the sister group to all other solenogasters, congruent with earlier ideas of a small-bodied ancestor of Solenogastres. In contrast, Bayesian Inference analyses support the large-bodied family Amphimeniidae as the sister group to all other solenogasters. Investigation of phylogenetic signal by comparing site-wise likelihood scores for the two competing hypotheses support the Meiomeniidae-first topology. In light of these results, we performed ancestral character state reconstruction to explore the implications of both hypotheses on understanding of Solenogaster evolution and review previous hypotheses about body size evolution and its potential consequences for solenogaster biology. Both hypotheses imply that body size evolution has been highly dynamic over the course of solenogaster evolution and that their relatively static body plan has successfully allowed for evolutionary transitions between meio-, macro- and megafaunal size ranges.
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Affiliation(s)
| | | | - Nickellaus G Roberts
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, USA
| | - Katharina M Jörger
- SNSB-Bavarian State Collection for Zoology, Section Mollusca, Munich, Germany
| | - Kevin M Kocot
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, USA; Alabama Museum of Natural History, The University of Alabama, Tuscaloosa, AL, USA.
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2
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Slyusarev GS, Bondarenko NI, Skalon EK, Rappoport AK, Radchenko D, Starunov VV. The structure of the muscular and nervous systems of the orthonectid Rhopalura litoralis (Orthonectida) or what parasitism can do to an annelid. ORG DIVERS EVOL 2021. [DOI: 10.1007/s13127-021-00519-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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3
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Sachslehner A, Zieger E, Calcino A, Wanninger A. HES and Mox genes are expressed during early mesoderm formation in a mollusk with putative ancestral features. Sci Rep 2021; 11:18030. [PMID: 34504115 PMCID: PMC8429573 DOI: 10.1038/s41598-021-96711-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 08/13/2021] [Indexed: 11/08/2022] Open
Abstract
The mesoderm is considered the youngest of the three germ layers. Although its morphogenesis has been studied in some metazoans, the molecular components underlying this process remain obscure for numerous phyla including the highly diverse Mollusca. Here, expression of Hairy and enhancer of split (HES), Mox, and myosin heavy chain (MHC) was investigated in Acanthochitona fascicularis, a representative of Polyplacophora with putative ancestral molluscan features. While AfaMHC is expressed throughout myogenesis, AfaMox1 is only expressed during early stages of mesodermal band formation and in the ventrolateral muscle, an autapomorphy of the polyplacophoran trochophore. Comparing our findings to previously published data across Metazoa reveals Mox expression in the mesoderm in numerous bilaterians including gastropods, polychaetes, and brachiopods. It is also involved in myogenesis in molluscs, annelids, tunicates, and craniates, suggesting a dual role of Mox in mesoderm and muscle formation in the last common bilaterian ancestor. AfaHESC2 is expressed in the ectoderm of the polyplacophoran gastrula and later in the mesodermal bands and in putative neural tissue, whereas AfaHESC7 is expressed in the trochoblasts of the gastrula and during foregut formation. This confirms the high developmental variability of HES gene expression and demonstrates that Mox and HES genes are pleiotropic.
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Affiliation(s)
- Attila Sachslehner
- Department of Evolutionary Biology, Unit for Integrative Zoology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria
| | - Elisabeth Zieger
- Department of Evolutionary Biology, Unit for Integrative Zoology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria
| | - Andrew Calcino
- Department of Evolutionary Biology, Unit for Integrative Zoology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria
| | - Andreas Wanninger
- Department of Evolutionary Biology, Unit for Integrative Zoology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
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4
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Zieger E, Calcino AD, Robert NSM, Baranyi C, Wanninger A. Ecdysis-related neuropeptide expression and metamorphosis in a non-ecdysozoan bilaterian. Evolution 2021; 75:2237-2250. [PMID: 34268730 DOI: 10.1111/evo.14308] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 06/22/2021] [Accepted: 06/29/2021] [Indexed: 12/28/2022]
Abstract
Ecdysis-related neuropeptides (ERNs), including eclosion hormone, crustacean cardioactive peptide, myoinhibitory peptide, bursicon alpha, and bursicon beta regulate molting in insects and crustaceans. Recent evidence further revealed that ERNs likely play an ancestral role in invertebrate life cycle transitions, but their tempo-spatial expression patterns have not been investigated outside Arthropoda. Using RNA-seq and in situ hybridization, we show that ERNs are broadly expressed in the developing nervous system of a mollusk, the polyplacophoran Acanthochitona fascicularis. While some ERN-expressing neurons persist from larval to juvenile stages, others are only present during settlement and metamorphosis. These transient neurons belong to the "ampullary system," a polyplacophoran-specific larval sensory structure. Surprisingly, however, ERN expression is absent from the apical organ, another larval sensory structure that degenerates before settlement is completed in A. fascicularis. Our findings thus support a role of ERNs in A. fascicularis metamorphosis but contradict the common notion that the apical organ-like structures shared by various aquatic invertebrates (i.e., cnidarians, annelids, mollusks, echinoderms) are of general importance for this process.
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Affiliation(s)
- Elisabeth Zieger
- Department of Evolutionary Biology, Unit for Integrative Zoology, University of Vienna, Vienna, Austria
| | - Andrew D Calcino
- Department of Evolutionary Biology, Unit for Integrative Zoology, University of Vienna, Vienna, Austria
| | - Nicolas S M Robert
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna, Austria
| | - Christian Baranyi
- Department of Evolutionary Biology, Unit for Integrative Zoology, University of Vienna, Vienna, Austria
| | - Andreas Wanninger
- Department of Evolutionary Biology, Unit for Integrative Zoology, University of Vienna, Vienna, Austria
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5
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von Döhren J. Diversity in the Development of the Neuromuscular System of Nemertean Larvae (Nemertea, Spiralia). Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.654846] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In studies on the development of nervous systems and musculature, fluorescent labeling of neuroactive substances and filamentous actin (f-actin) of muscle cells and the subsequent analysis with confocal laser scanning microscopy (CLSM), has led to a broad comparative data set for the majority of the clades of the superphylum Spiralia. However, a number of clades remain understudied, which results in gaps in our knowledge that drastically hamper the formulation of broad-scale hypotheses on the evolutionary developmental biology (EvoDevo) of the structures in question. Regarding comparative data on the development of the peptidergic nervous system and the musculature of species belonging to the spiralian clade Nemertea (ribbon worms), such considerable knowledge gaps are manifest. This paper presents first findings on fluorescent labeling of the FMRFamide-like component of the nervous system and contributes additional data on the muscle development in the presently still underrepresented larvae of palaeo- and hoplonemertean species. Whereas the architecture of the FMRFamide-like nervous system is comparably uniform between the studied representatives, the formation of the musculature differs considerably, exhibiting developmental modes yet undescribed for any spiralian species. The presented results fill a significant gap in the spiralian EvoDevo data set and thus allow for further elaboration of hypotheses on the ancestral pattern of the musculature and a prominent component of the nervous system in Nemertea. However, with respect to the variety observed, it is expected that the true diversity of the developmental pathways is still to be discovered when more detailed data on other nemertean species will be available.
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Kocot KM, Todt C, Mikkelsen NT, Halanych KM. Phylogenomics of Aplacophora (Mollusca, Aculifera) and a solenogaster without a foot. Proc Biol Sci 2020; 286:20190115. [PMID: 31064303 PMCID: PMC6532501 DOI: 10.1098/rspb.2019.0115] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Recent molecular phylogenetic investigations strongly supported the placement of the shell-less, worm-shaped aplacophoran molluscs (Solenogastres and Caudofoveata) and chitons (Polyplacophora) in a clade called Aculifera, which is the sister taxon of all other molluscs. Thus, understanding the evolutionary history of aculiferan molluscs is important for understanding early molluscan evolution. In particular, fundamental questions about evolutionary relationships within Aplacophora have long been unanswered. Here, we supplemented the paucity of available data with transcriptomes from 25 aculiferans and conducted phylogenomic analyses on datasets with up to 525 genes and 75 914 amino acid positions. Our results indicate that aplacophoran taxonomy requires revision as several traditionally recognized groups are non-monophyletic. Most notably, Cavibelonia, the solenogaster taxon defined by hollow sclerites, is polyphyletic, suggesting parallel evolution of hollow sclerites in multiple lineages. Moreover, we describe Apodomenia enigmatica sp. nov., a bizarre new species that appears to be a morphological intermediate between Solenogastres and Caudofoveata. This animal is not a missing link, however; molecular and morphological studies show that it is a derived solenogaster that lacks a foot, mantle cavity and radula. Taken together, these results shed light on the evolutionary history of Aplacophora and reveal a surprising degree of morphological plasticity within the group.
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Affiliation(s)
- Kevin M Kocot
- 1 The University of Alabama and the Alabama Museum of Natural History , 500 Hackberry Lane, Tuscaloosa, AL 35487 , USA
| | - Christiane Todt
- 2 Rådgivende Biologer AS , Edvard Griegs vei 3, 5059 Bergen , Norway
| | - Nina T Mikkelsen
- 3 University Museum of Bergen, The Natural History Collections, University of Bergen , Allégaten 41, 5007 Bergen , Norway
| | - Kenneth M Halanych
- 4 Department of Biological Sciences, Auburn University , Auburn, AL 36849 , USA
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7
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Irisarri I, Uribe JE, Eernisse DJ, Zardoya R. A mitogenomic phylogeny of chitons (Mollusca: Polyplacophora). BMC Evol Biol 2020; 20:22. [PMID: 32024460 PMCID: PMC7003433 DOI: 10.1186/s12862-019-1573-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 12/30/2019] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Polyplacophora, or chitons, have long fascinated malacologists for their distinct and rather conserved morphology and lifestyle compared to other mollusk classes. However, key aspects of their phylogeny and evolution remain unclear due to the few morphological, molecular, or combined phylogenetic analyses, particularly those addressing the relationships among the major chiton lineages. RESULTS Here, we present a mitogenomic phylogeny of chitons based on 13 newly sequenced mitochondrial genomes along with eight available ones and RNAseq-derived mitochondrial sequences from four additional species. Reconstructed phylogenies largely agreed with the latest advances in chiton systematics and integrative taxonomy but we identified some conflicts that call for taxonomic revisions. Despite an overall conserved gene order in chiton mitogenomes, we described three new rearrangements that might have taxonomic utility and reconstructed the most likely scenario of gene order change in this group. Our phylogeny was time-calibrated using various fossils and relaxed molecular clocks, and the robustness of these analyses was assessed with several sensitivity analyses. The inferred ages largely agreed with previous molecular clock estimates and the fossil record, but we also noted that the ambiguities inherent to the chiton fossil record might confound molecular clock analyses. CONCLUSIONS In light of the reconstructed time-calibrated framework, we discuss the evolution of key morphological features and call for a continued effort towards clarifying the phylogeny and evolution of chitons.
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Affiliation(s)
- Iker Irisarri
- Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (MNCN-CSIC), c/ José Gutiérrez Abascal 2, 28006, Madrid, Spain.
- Department of Organismal Biology (Systematic Biology Program), Evolutionary Biology Centre, Uppsala University, Norbyv. 18C, 75236, Uppsala, Sweden.
| | - Juan E Uribe
- Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (MNCN-CSIC), c/ José Gutiérrez Abascal 2, 28006, Madrid, Spain
- Department of Invertebrate Zoology, Smithsonian Institution, National Museum of Natural History, 10th St. & Constitutional Ave. NW, Washington, DC, 20560, USA
| | - Douglas J Eernisse
- Department of Biological Science, California State University Fullerton, 800 N. State College Blvd, Fullerton, CA, 92831-3599, USA
| | - Rafael Zardoya
- Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (MNCN-CSIC), c/ José Gutiérrez Abascal 2, 28006, Madrid, Spain
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8
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Chernyshev AV, Kajihara H. Comparative muscular morphology in Archinemertea (Nemertea: Palaeonemertea). ZOOMORPHOLOGY 2019. [DOI: 10.1007/s00435-019-00440-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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9
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Wanninger A, Wollesen T. The evolution of molluscs. Biol Rev Camb Philos Soc 2019; 94:102-115. [PMID: 29931833 PMCID: PMC6378612 DOI: 10.1111/brv.12439] [Citation(s) in RCA: 87] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 05/25/2018] [Accepted: 05/31/2018] [Indexed: 01/24/2023]
Abstract
Molluscs are extremely diverse invertebrate animals with a rich fossil record, highly divergent life cycles, and considerable economical and ecological importance. Key representatives include worm-like aplacophorans, armoured groups (e.g. polyplacophorans, gastropods, bivalves) and the highly complex cephalopods. Molluscan origins and evolution of their different phenotypes have largely remained unresolved, but significant progress has been made over recent years. Phylogenomic studies revealed a dichotomy of the phylum, resulting in Aculifera (shell-less aplacophorans and multi-shelled polyplacophorans) and Conchifera (all other, primarily uni-shelled groups). This challenged traditional hypotheses that proposed that molluscs gradually evolved complex phenotypes from simple, worm-like animals, a view that is corroborated by developmental studies that showed that aplacophorans are secondarily simplified. Gene expression data indicate that key regulators involved in anterior-posterior patterning (the homeobox-containing Hox genes) lost this function and were co-opted into the evolution of taxon-specific novelties in conchiferans. While the bone morphogenetic protein (BMP)/decapentaplegic (Dpp) signalling pathway, that mediates dorso-ventral axis formation, and molecular components that establish chirality appear to be more conserved between molluscs and other metazoans, variations from the common scheme occur within molluscan sublineages. The deviation of various molluscs from developmental pathways that otherwise appear widely conserved among metazoans provides novel hypotheses on molluscan evolution that can be tested with genome editing tools such as the CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeats-associated protein9) system.
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Affiliation(s)
- Andreas Wanninger
- Department of Integrative ZoologyUniversity of ViennaAlthanstrasse 14, 1090 ViennaAustria
| | - Tim Wollesen
- Department of Integrative ZoologyUniversity of ViennaAlthanstrasse 14, 1090 ViennaAustria
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10
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Molecular phylogeny of Caudofoveata (Mollusca) challenges traditional views. Mol Phylogenet Evol 2018; 132:138-150. [PMID: 30423439 DOI: 10.1016/j.ympev.2018.10.037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 07/23/2018] [Accepted: 10/30/2018] [Indexed: 11/22/2022]
Abstract
The shell-less, worm-shaped Caudofoveata (=Chaetodermomorpha) is one of the least known groups of molluscs. The taxon consists of 141 recognized species found from intertidal environments to the deep-sea where they live burrowing in sediment. Evolutionary relationships of the group have been debated, but few studies based on morphological or molecular data have investigated the phylogeny of the group. Here we use molecular phylogenetics to resolve relationships among and within families of Caudofoveata. Phylogenetic analyses were performed using selected mitochondrial and nuclear genes from species from all recognized families of Caudofoveata. In resulting trees and contrary to traditional views, Prochaetodermatidae forms the sister clade to a clade containing the other two currently recognized families, Chaetodermatidae and Limifossoridae. The monophyly of Prochaetodermatidae is highly supported, but Limifossoridae and Chaetodermatidae are not recovered as monophyletic. Most of the caudofoveate genera are also not recovered as monophyletic in our analyses. Thus results from our molecular data suggest that the current classification of Caudofoveata is in need of revision, and indicate evolutionary scenarios that differ from previously proposed hypotheses based on morphology.
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11
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Mikkelsen NT, Kocot KM, Halanych KM. Mitogenomics reveals phylogenetic relationships of caudofoveate aplacophoran molluscs. Mol Phylogenet Evol 2018; 127:429-436. [PMID: 29702218 DOI: 10.1016/j.ympev.2018.04.031] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 01/16/2018] [Accepted: 04/20/2018] [Indexed: 11/28/2022]
Abstract
The worm-shaped, shell-less aplacophoran molluscs Caudofoveata and Solenogastres have recently received attention as part of the clade Aculifera, but relationships within these two lineages are still largely unknown. Here, we use complete mitochondrial genomes to shed light on higher-level relationships within Caudofoveata. Mitochondrial genomes have been sequenced for many diverse molluscs, but only two mitochondrial genomes from aplacophoran molluscs (the caudofoveates Scutopus ventrolineatus and Chaetoderma nitidulum) are available to date. We sequenced and assembled complete or near complete mitochondrial genomes of five additional species of Caudofoveata (Falcidens acutargatus, Falcidens halanychi, Scutopus robustus, Psilodens balduri and Spathoderma clenchi) and one species of Solenogastres (Neomenia carinata) for comparison to available mitochondrial genomes of aculiferans. Comparison of mitochondrial gene order among different lineages revealed a highly conserved order of protein coding genes corresponding to the hypothesized ancestral gene order for Mollusca. Unique arrangements of tRNAs were found among lineages of aculiferan molluscs as well as among caudofoveate taxa. Phylogenetic analyses of amino acid sequences for the 13 protein-coding genes recovered a monophyletic Aplacophora. Within Caudofoveata, Chaetodermatidae, but not Limifossoridae, was recovered monophyletic. Taken together, our results suggest that mitochondrial genomes can serve as useful molecular markers for aculiferan phylogenetics, especially for more recent phylogenetic events.
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Affiliation(s)
- Nina T Mikkelsen
- University Museum of Bergen, University of Bergen, 5020 Bergen, Norway; Department of Biology, University of Bergen, 5020 Bergen, Norway.
| | - Kevin M Kocot
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA; Department of Biological Sciences and Alabama Museum of Natural History, The University of Alabama, Tuscaloosa, AL 35487, USA(1)
| | - Kenneth M Halanych
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA
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12
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Pavlicek A, Schwaha T, Wanninger A. Towards a ground pattern reconstruction of bivalve nervous systems: neurogenesis in the zebra mussel Dreissena polymorpha. ORG DIVERS EVOL 2018; 18:101-114. [PMID: 31258414 PMCID: PMC6566206 DOI: 10.1007/s13127-017-0356-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 12/28/2017] [Indexed: 12/03/2022]
Abstract
Bivalvia is a taxon of aquatic mollusks that includes clams, oysters, mussels, and scallops. Within heterodont bivalves, Dreissena polymorpha is a small, mytiliform, freshwater mussel that develops indirectly via a planktotrophic veliger larva. Currently, only a few studies on bivalve neurogenesis are available, impeding the reconstruction of a ground pattern in Bivalvia. In order to inject novel data into this discussion, we describe herein the development of the serotonin-like and α-tubulin-like immunoreactive (lir) neuronal components of D. polymorpha from the early trochophore to the late veliger stage. Neurogenesis starts in the early trochophore stage at the apical pole with the appearance of one flask-shaped serotonin-lir cell. When larvae reach the veliger stage, four flask-shaped serotonin-lir cells are present in the apical organ. At the same time, the anlagen of the cerebral ganglia start to form at the base of the apical organ. From the apical organ, one pair of cerebro-visceral connectives projects posteriorly and connects to a posterior larval sensory organ that contains serotonin- and α-tubulin-like flask-shaped cells. Additional, paired serotonin-lir neurites originate from the apical organ and project into the velum. One unpaired stomatogastric serotonin-lir cell develops ventrally to the stomach at the veliger stage. The low number of serotonin-lir cells in the apical organ of bivalve veligers is shared with larvae of basally branching gastropods and scaphopods and is thus considered a feature of the last common ancestor of Conchifera, while the overall simplicity of the larval neural architecture appears to be a specific trait of Bivalvia.
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Affiliation(s)
- Anna Pavlicek
- Department of Integrative Zoology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Thomas Schwaha
- Department of Integrative Zoology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Andreas Wanninger
- Department of Integrative Zoology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
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13
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Özpolat BD, Handberg-Thorsager M, Vervoort M, Balavoine G. Cell lineage and cell cycling analyses of the 4d micromere using live imaging in the marine annelid Platynereis dumerilii. eLife 2017; 6:30463. [PMID: 29231816 PMCID: PMC5764573 DOI: 10.7554/elife.30463] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Accepted: 12/11/2017] [Indexed: 11/13/2022] Open
Abstract
Cell lineage, cell cycle, and cell fate are tightly associated in developmental processes, but in vivo studies at single-cell resolution showing the intricacies of these associations are rare due to technical limitations. In this study on the marine annelid Platynereis dumerilii, we investigated the lineage of the 4d micromere, using high-resolution long-term live imaging complemented with a live-cell cycle reporter. 4d is the origin of mesodermal lineages and the germline in many spiralians. We traced lineages at single-cell resolution within 4d and demonstrate that embryonic segmental mesoderm forms via teloblastic divisions, as in clitellate annelids. We also identified the precise cellular origins of the larval mesodermal posterior growth zone. We found that differentially-fated progeny of 4d (germline, segmental mesoderm, growth zone) display significantly different cell cycling. This work has evolutionary implications, sets up the foundation for functional studies in annelid stem cells, and presents newly established techniques for live imaging marine embryos.
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14
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Wollesen T, Scherholz M, Rodríguez Monje SV, Redl E, Todt C, Wanninger A. Brain regionalization genes are co-opted into shell field patterning in Mollusca. Sci Rep 2017; 7:5486. [PMID: 28710480 PMCID: PMC5511173 DOI: 10.1038/s41598-017-05605-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 05/31/2017] [Indexed: 12/14/2022] Open
Abstract
The 'brain regionalization genes' Six3/6, Otx, Pax2/5/8, Gbx, and Hox1 are expressed in a similar fashion in the deuterostome, ecdysozoan, and the cephalopod brain, questioning whether this holds also true for the remaining Mollusca. We investigated developmental Gbx-expression in representatives of both molluscan sister groups, the Aculifera and Conchifera. Gbx is expressed in the posterior central nervous system of an aculiferan polyplacophoran and solenogaster but not in a conchiferan bivalve suggesting that Gbx, together with Six3/6, Otx, Pax2/5/8, and Hox1, is involved in central nervous system regionalization as reported for other bilaterians. Gbx is, however, also expressed in the anterior central nervous system, i.e. the anlagen of the cerebral ganglia, in the solenogaster, a condition not reported for any other bilaterian so far. Strikingly, all Gbx-orthologs and the other 'posterior brain regionalization genes' such as Pax2/5/8 and Hox1 are expressed in the mantle that secretes shell(s) and spicules of mollusks (except cephalopods). In bivalves, the ancestral condition has even been lost, with Gbx and Pax2/5/8 not being expressed in the developing central nervous system anymore. This suggests an additional role in the formation of the molluscan shell field(s) and spicule-bearing cells, key features of mollusks.
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Affiliation(s)
- Tim Wollesen
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090, Vienna, Austria.
| | - Maik Scherholz
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090, Vienna, Austria
| | - Sonia Victoria Rodríguez Monje
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090, Vienna, Austria
| | - Emanuel Redl
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090, Vienna, Austria
| | - Christiane Todt
- University Museum of Bergen, University of Bergen, Allégaten 41, 5007, Bergen, Norway
| | - Andreas Wanninger
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090, Vienna, Austria
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Scherholz M, Redl E, Wollesen T, de Oliveira AL, Todt C, Wanninger A. Ancestral and novel roles of Pax family genes in mollusks. BMC Evol Biol 2017; 17:81. [PMID: 28302062 PMCID: PMC5356317 DOI: 10.1186/s12862-017-0919-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 02/18/2017] [Indexed: 01/31/2023] Open
Abstract
Background Pax genes are transcription factors with significant roles in cell fate specification and tissue differentiation during animal ontogeny. Most information on their tempo-spatial mode of expression is available from well-studied model organisms where the Pax-subfamilies Pax2/5/8, Pax6, and Paxα/β are mainly involved in the development of the central nervous system (CNS), the eyes, and other sensory organs. In certain taxa, Pax2/5/8 seems to be additionally involved in the development of excretion organs. Data on expression patterns in lophotrochozoans, and in particular in mollusks, are very scarce for all the above-mentioned Pax-subfamilies, which hampers reconstruction of their putative ancestral roles in bilaterian animals. Thus, we studied the developmental expression of Pax2/5/8, Pax6, and the lophotrochozoan-specific Paxβ in the worm-shaped mollusk Wirenia argentea, a member of Aplacophora that together with Polyplacophora forms the Aculifera, the proposed sister taxon to all primarily single-shelled mollusks (Conchifera). Results All investigated Pax genes are expressed in the developing cerebral ganglia and in the ventral nerve cords, but not in the lateral nerve cords of the tetraneural nervous system. Additionally, Pax2/5/8 is expressed in epidermal spicule-secreting or associated cells of the larval trunk and in the region of the developing protonephridia. We found no indication for an involvement of the investigated Pax genes in the development of larval or adult sensory organs of Wirenia argentea. Conclusions Pax2/5/8 seems to have a conserved role in the development of the CNS, whereas expression in the spicule-secreting tissues of aplacophorans and polyplacophorans suggests co-option in aculiferan skeletogenesis. The Pax6 expression pattern in Aculifera largely resembles the common bilaterian expression during CNS development. All data available on Paxβ expression argue for a common role in lophotrochozoan neurogenesis. Electronic supplementary material The online version of this article (doi:10.1186/s12862-017-0919-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Maik Scherholz
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090, Vienna, Austria
| | - Emanuel Redl
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090, Vienna, Austria
| | - Tim Wollesen
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090, Vienna, Austria
| | - André Luiz de Oliveira
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090, Vienna, Austria
| | - Christiane Todt
- University Museum of Bergen, University of Bergen, Allégaten 41, 5007, Bergen, Norway
| | - Andreas Wanninger
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstraße 14, 1090, Vienna, Austria.
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Redl E, Scherholz M, Wollesen T, Todt C, Wanninger A. Cell Proliferation Pattern and Twist Expression in an Aplacophoran Mollusk Argue Against Segmented Ancestry of Mollusca. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2016; 326:422-436. [PMID: 27966274 PMCID: PMC5299467 DOI: 10.1002/jez.b.22714] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 10/28/2016] [Accepted: 11/02/2016] [Indexed: 01/12/2023]
Abstract
The study of aplacophoran mollusks (i.e., Solenogastres or Neomeniomorpha and Caudofoveata or Chaetodermomorpha) has traditionally been regarded as crucial for reconstructing the morphology of the last common ancestor of the Mollusca. Since their proposed close relatives, the Polyplacophora, show a distinct seriality in certain organ systems, the aplacophorans are also in the focus of attention with regard to the question of a potential segmented ancestry of mollusks. To contribute to this question, we investigated cell proliferation patterns and the expression of the twist ortholog during larval development in solenogasters. In advanced to late larvae, during the outgrowth of the trunk, a pair of longitudinal bands of proliferating cells is found subepithelially in a lateral to ventrolateral position. These bands elongate during subsequent development as the trunk grows longer. Likewise, expression of twist occurs in two laterally positioned, subepithelial longitudinal stripes in advanced larvae. Both, the pattern of proliferating cells and the expression domain of twist demonstrate the existence of extensive and long‐lived mesodermal bands in a worm‐shaped aculiferan, a situation which is similar to annelids but in stark contrast to conchiferans, where the mesodermal bands are usually rudimentary and ephemeral. Yet, in contrast to annelids, neither the bands of proliferating cells nor the twist expression domain show a separation into distinct serial subunits, which clearly argues against a segmented ancestry of mollusks. Furthermore, the lack of twist expression during the development of the ventromedian muscle argues against homology of a ventromedian longitudinal muscle in protostomes with the notochord of chordates.
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Affiliation(s)
- Emanuel Redl
- Faculty of Life Sciences, Department of Integrative Zoology, University of Vienna, Vienna, Austria
| | - Maik Scherholz
- Faculty of Life Sciences, Department of Integrative Zoology, University of Vienna, Vienna, Austria
| | - Tim Wollesen
- Faculty of Life Sciences, Department of Integrative Zoology, University of Vienna, Vienna, Austria
| | - Christiane Todt
- University Museum, The Natural History Collections, University of Bergen, Bergen, Norway
| | - Andreas Wanninger
- Faculty of Life Sciences, Department of Integrative Zoology, University of Vienna, Vienna, Austria
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Audino JA, Marian JEAR, Kristof A, Wanninger A. Inferring muscular ground patterns in Bivalvia: Myogenesis in the scallop Nodipecten nodosus. Front Zool 2015; 12:34. [PMID: 26635889 PMCID: PMC4668623 DOI: 10.1186/s12983-015-0125-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 11/05/2015] [Indexed: 11/26/2022] Open
Abstract
Background Myogenesis is currently investigated in a number of invertebrate taxa using combined techniques, including fluorescence labeling, confocal microscopy, and 3D imaging, in order to understand anatomical and functional issues and to contribute to evolutionary questions. Although developmental studies on the gross morphology of bivalves have been extensively pursued, organogenesis including muscle development has been scarcely investigated so far. Results The present study describes in detail myogenesis in the scallop Nodipecten nodosus (Linnaeus, 1758) during larval and postmetamorphic stages by means of light, electron, and confocal microscopy. The veliger muscle system consists of an anterior adductor muscle, as well as four branched pairs of striated velum retractors and two pairs of striated ventral larval retractors. The pediveliger stage exhibits a considerably elaborated musculature comprising the velum retractors, the future adult foot retractor, mantle (pallial) muscles, and the anterior and posterior adductors, both composed of smooth and striated portions. During metamorphosis, all larval retractors together with the anterior adductor degenerate, resulting in the adult monomyarian condition, whereby the posterior adductor retains both myofiber types. Three muscle groups, i.e., the posterior adductor, foot retractor, and pallial muscles, have their origin prior to metamorphosis and are subsequently remodeled. Conclusions Our data suggest a dimyarian condition (i.e., the presence of an anterior and a posterior adductor in the adult) as the basal condition for pectinids. Comparative analysis of myogenesis across Bivalvia strongly argues for ontogenetic and evolutionary independence of larval retractors from the adult musculature, as well as a complex set of larval retractor muscles in the last common bivalve ancestor. Electronic supplementary material The online version of this article (doi:10.1186/s12983-015-0125-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jorge A Audino
- Department of Zoology, University of São Paulo, Rua do Matão, Travessa 14, 101, 05508-090 São Paulo, Brazil
| | - José Eduardo A R Marian
- Department of Zoology, University of São Paulo, Rua do Matão, Travessa 14, 101, 05508-090 São Paulo, Brazil
| | - Alen Kristof
- Department of Integrative Zoology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Andreas Wanninger
- Department of Integrative Zoology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
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